<p>The Chaco golden knee tarantula is one of the larger species of tarantula. Adult spiders can have a seven-inch legspan.</p>

The Chaco golden knee tarantula is one of the larger species of tarantula. Adult spiders can have a seven-inch legspan.

Photograph by Joel Sartore, National Geographic Photo Ark

Spiders

Spiders are arachnids, a class of arthropods that also includes scorpions, mites, and ticks. There are more than 45,000 known species of spiders, found in habitats all over the world. There’s a spider with a cartoonish butt, spiders that can jump on demand, and cannibal spiders that look like pelicans.

Spiders range in size from the tiny Samoan moss spider, which is .011 inch long, to the massive Goliath birdeater, a tarantula with a leg span of almost a foot.

For most people, the thought of spiders conjures up images of tarantulas, wolf spiders, and other (seemingly) fearsome creatures. Though all spiders have venom to one degree or another, only a handful are dangerous to

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